Multi-Touch Modes

Single, Dual and Multi Touch Overview

Lumio's Crystal To Touch^TM touch screens can operate in a range of different modes depending on hardware and software configuration. This document provides an overview of the hardware requirements and touch functionality of the different modes. Detailed descriptions of the software and driver interfaces can be found in the appropriate interface specification documents which are available from Lumio on request.

The Crystal Touch^TM touch screens can be broken into four categories:

SingleTouch
Dual Control (often referred to incorrectly by others as Dual Touch)
DualTouch
True Multi-point touch referred to simply as Multi Touch

The main differences in hardware and interfaces can be summarized as follows:

1. Single Touch

Hardware: Two Sensor Modules, three sided Active-Barrier^TM illumination and Single Touch Controller
Software interface: USB HID Mouse events

2. Dual Control

Hardware: Two Sensor Modules, three sided Active-Barrrier^TM illumination and Dual Control Controller
Software interface: USB HID Mouse & Keyboard events or USB via Crystal TouchTM Manager

3. Dual Touch

Hardware: Two Sensor Modules, three sided Active-Barrrier^TM illumination and Dual Touch Controller
Software interface: Serial RS232 and Lumio Crystal Touch^TM Driver

4. Multi Touch

Hardware: Four or more Sensor Modules, four sided Active-Barrier^TM illumination and Multi Touch Controller
Software interface: Serial RS232 and Lumio Crystal Touch^TM Driver

The following sections describe performance of each of these operation modes.

Lumio Touchscreens White Paper

Klony Lieberman

Lumio Inc., 5 Nahum Hefzadi st. Beit Ofer, Jerusalem, Israel

A novel, edge emitting plastic optical fiber element has been developed to efficiently generate thin, planar light fields adjacent to a touch surface. This fiber element, referred to as an Active-Barrier^TMis placed at the edge of the touch surface along three sides, illuminating a thin layer just above the surface. High speed, high resolution linear optical sensors are placed along the fourth side of the touch surface to sense interactions with the light field. Both the illumination fibers and the sensors are embedded in a thin frame, a few millimeters high, which can be bonded directly to a display glass or table top. The optical efficiency of the Active-Barrier^TMfiber enables the sensing frame to be scaled up to cover very large interaction regions. Multi-touch operation is also supported by incorporation of redundant sensors

and/or detection zone separation.

1. Introduction

Optical imaging is the method of choice for touch activating medium and large scale surfaces. This is primarily a result of the scalability of optical techniques when compared to physical overlays whose cost grows exponentially as the size of the interaction area increases as a consequence of, among other things, yield issues. Additional benefits include the fact that as a completely digital solution optical imaging is free from the drift and aging that plague resistive and capacitive technologies so systems never needs to be recalibrated. A fast sensor response time minimizes latency and a high frame rate coupled with high optical resolution provides the performance required for high end sensing applications such as graphic stylus input and jitter free cursor control.

Optical sensing techniques can be divided into two categories which depending on the geometry of the detection. In-plane sensing techniques use illumination and sensing components that lie, as the name suggests, within the touch sensing plane - i.e. just above the sensing surface. Out-of-plane sensing techniques on the other hand rely on two dimensional imaging sensors that view the sensing plane from above or below the interaction surface. Out-of-plane techniques have the advantage that they inherently support multi-touch sensing since each location on the image sensor corresponds directly to a unique location on the interaction surface but are limited in their usefulness due to the geometrical viewing constraints requiring large volumes to be freed up on one side of the surface to obtain an unobstructed view of the entire sensing region. The 2D sensors are also more expensive for a given resolution and typically do not support high frame rates. In-plane sensing on the other hand can be embedded in a thin frame that surrounds the interaction region but requires more sophisticated algorithmic and hardware support in order to track more than one event at a time. The linear sensors used for in-plane sensing can also provide much higher resolutions and frame rates. Both techniques scale economically to very large sizes.

In this paper we describe the underlying technology that enables Lumio's in-plane optical touch frame and the techniques that are employed to support multi-touch interaction.